During late 1970s and early 1980s, the importance of a reliable bench-scale engineering tool for measuring heat release rate was being realized. A number of such devices had already been built. None was felt to be appropriate for normal engineering laboratory use. The problems were two-fold: errors in measurement and difficulty of operation. Insulated box (sensible enthalpy) types of designs were demonstrated to show large systematic errors. Instruments built on other measurement principles, such as substitution burner, were capable of good accuracy but were very complex and difficult to install and maintain. This indicated that an instrument of a new design was needed.
Several years of exploratory research on various instrument designs were conducted. The successful design was termed the Cone calorimeter and was first described in an NBS report in 1982. Depending on the specific application, tests can determine combustion characteristics such as ignition times, mass loss, heat and smoke release rates, heat of combustion and the average specific extinction area. The Cone calorimeter test is at present the most advanced method for assessing materials reaction to fire. The method follows the procedure given in international standard ISO 5660-1:1993(E).
Test apparatuses approved by ASTM International, Inc. for measuring the combustive properties and behavior of materials or objects, such as the Cone calorimeter and the Fire Propagation Apparatus, irradiate a specimen of a material or an object with a known infrared (IR) heat flux from a radiant heating source. The specimen is typically coated with paint or a carbon mixture to improve absorption of the radiant heat flux in order to simulate heat absorption during an actual fire, when the material or object becomes covered with soot and thereby absorbs most of the radiant energy incident upon it. The incident heat flux from the radiant heater is often taken as a measure of the heat flux required to cause the detectable condition or response, such as ignition, of the material or object. However, because of the coating, not all of the heat flux incident on the coating is absorbed by the specimen and the portion of the heat flux emanating from radiant heating source that is absorbed by the specimen varies from one coating to another. As a result, there is a problem evaluating and comparing test data from specimens having different coatings.
However, prior to the present invention, there was no standard apparatus for electronically measuring the width, length, and area of the burnt surface, the duration of flame after the removal of the piloted flame (fire endurance), back-darkening, back-holing, and back-firing times. For the purpose of determining the combustive behavior of a material, the duration of flame after the removal of the direct flame exposure would be necessary. Proper fire safety measures depend upon limitation of fire spread and growth, so it will be necessary to obtain a device that accurately measures fire spread patterns with high precision.
Furthermore, it is essential to measure the time it takes for the fire to penetrate from the front surface of the material, where it was exposed to, to the back surface (the opposite side of the specimen where the direct flame-exposure is carried out). Also, the direction of flame affects the burning behavior of materials; it will therefore be vital to have a device that can do the flame-exposure testing in different directions and analyze the effects for each.
In the meantime, not all researches can be carried out with great expenses of providing large specimens as it is required in Steiner Tunnel, ULI 723, and full-scale furnaces (ASTM E-119; NFPA 251 & 2; ISO 834); so, it would also be helpful to provide apparatus and method that work with small-size specimens. Also, the coating of specimens with paint or carbon mixture may affect the final results and analysis; it should therefore be necessary to provide methods and devices that do not need the specimens to be coated before the testing procedures.
Therefore, it would be advantageous to provide an apparatus for overcoming the above shortcomings of the prior art.